1. Field of the Invention
This invention relates to an electromechanical translation apparatus and more particularly to a piezoelectric translation apparatus used as a piezoelectric multiaxis micropositioner wherein piezoelectric driver assemblies selectively incrementally advance a means defining a driven member, such as a spherical segment or planar member, in a selected direction over a predetermined path in incremental, programmed steps. The preferred embodiment of the piezoelectric translation apparatus is to incrementally adjust a planar mirror affixed to a spherical member to control the angle of deflection in an optical path.
2. Description of the Prior Art
The concept of a piezoelectric motor or an electro- mechanical device to produce rotational or linear relative movement between an electromechanical device and a driven member is known in the art.
A reversible motor with a piezoelectric rotor drive having a two-tier piezoelectric driving transducer which is driven by an oscillator and a phase shifter for high speed reverse operation is disclosed in Russian Pat. No. SU-651-434. In this reversible motor, the two-tier transducer is arranged in a coplanar, stacked arrangement and has a common electrode in the adjacent opposed surfaces. The outer surface of each piezoelectric element has an electrode affixed thereto. An oscillator drives one piezoelectric element in contact with a shaft in a first direction and a second piezoelectric element, which is coupled to a housing and which supports the shaft for rotation, is driven by a phase shifter in a second direction producing relative movement between the shaft and housing which rotates the shaft. In this motor, the piezoelectric element directly clamps the exterior surface of the shaft.
A unidirectional piezoelectric motor having a wedge-shaped driving element which frictionally engages the exterior surface of a shaft to rotate the same in response to vibrations of a piezoelectric element coupled between the wedge-shaped driving element and housing which rotatably supports the shaft is disclosed in Russian Pat. No. SU-635-538.
The use of a piezoelectric electromechanical translation apparatus using a multi-section, axially aligned piezoelectric driver to produce linear motion between the piezoelectric electromechanical translation apparatus and a shaft is disclosed in U.S. Pat. Nos. 3,902,084 and 3,902,085. In each of these apparatus, the piezoelectric driver directly engages and clamps the shaft through electrodes formed on the surface of piezoelectric crystals in order to produce incremental, stepped movement between the apparatus and the shaft.
A piezoelectric motor for producing angular motion which is capable of being transmitted to a remotely disposed rotatable element wherein polyphase electric potentials are applied to a plurality of piezoelectric crystal elements which are so arranged and interconnected that the vibratory movements thereof are translated into the rotational movement is disclosed in U.S. Pat. No. 2,439,499.
A dynamic balancing machine for detecting the periodic forces of unbalance of a rotary body and yielding a visual or other indication of the magnitude and orientation of such forces utilizing a means for supporting each end of a rotating body to be tested upon a pair of piezoelectric quartz crystal plates as the pickup elements which are arranged in a "V" shaped support is disclosed in U.S. Pat. No. 2,461,645.
Another piezoelectric driving device having an elongated piezoelectric driving bar which is resiliently mounted to drive an intermediate rotor in response to vibrations of the piezoelectric crystal and wherein the intermediate rotor drives a main rotor is disclosed in Russian Pat. No. SU-636-760.
An electrical rotary apparatus utilizing four piezoelectric elements which are supported radially from and in an equally spaced relationship on a circular shaped housing and which are adapted to be expanded, in response to a magnetic field, to engage a shaft and wherein application of a AC signal to the piezoelectric element while in contact with the shaft causes relative movement between the housing and the shaft is disclosed in Russian Pat. No. SU-688-033.
U.S. Pat. No. 3,377,489 discloses a position control device which utilizes a piezoelectric material which, when subjected to an electrical potential, results in mechanical distortion of the material which is exhibited in either torsional movement or a variation of dimension. This patent also discloses that, in operation, one portion of the piezoelectric material is held in position during application of a voltage to cause mechanical distortion of the other portions. Thereafter, the moved or distorted portions of the material are locked into their distorted positions. Following the release of the first held portion and removal of the noted potential, the piezoelectric material reverts to its normal, nondistorted condition, but in a different location. The incremental movement of the piezoelectric material from one location to another may be used for accurate positioning functions.
U.S. Pat. No. 3,292,019 discloses a transducer which includes a piezoelectric member which is responsive to an alternating voltage potential being applied thereto causing an oscillatory motion of the piezoelectric member with a one-way clamp on either side of the expansion and contraction due to the oscillatory motion so that the expansion is permitted in one direction only due to clamping one end of the oscillating member and the contraction also results in movement in the same direction due to clamping of the other end of the oscillatory member.
U.S. Pat. No. 3,649,856 discloses a transducer for converting digital signals into linear motion. In the embodiment disclosed in this patent, the transducer is formed of a hollow cylinder made of ferroelectric ceramic material which is made to have piezoelectric properties. The cylinder will move along the inside wall of a linear tube in response to a voltage pattern commutated through annular rings on the inside of the hollow cylinder such that the voltage on a given ring increases in steps to a maximum and then decreases, with the result that the hollow cylinder contracts in circumferential and axial dimensions in annular sections progressively from one end to the other end in a direction of desired motion as the voltage pattern is commutated in that direction. A predetermined motion is achieved by one cycle of commutation. For further motion, the voltage pattern is commutated through additional cycles.
U.S. Pat. No. 3,684,904 discloses a device for precision displacement of a solid body with respect to a bearing surface wherein the device includes at least two supports of elastic material and each of the supports is originally fixed at one end thereof to a displaceable solid body. At least two drive means are provided for ensuring independent movement of the ends of each support, both in a direction perpendicular to the bearing surface in the direction of movement of the solid body.
U.S. Pat. No. 3,217,218 discloses an alternating energy control system which illustrates at FIG. 5 thereof an embodiment which utilizes a magnetostrictive rod. As shown in said FIG. 5, the magnetostrictive rod changes its dimension under the influence of a strong magnetic field, and it is the magnetostrictive rod which is an element to be moved incrementally. Movement is incurred by use of clamping members which are located at each end of the magnetostrictive rod. By controlling the clamping or relaxing of the various clamping members, and by controlling the application of an alternating electric current through a winding extending around the exterior of the magnetostrictive rod, the magnetostrictive rod is expanded. If one of the clamped pairs is energized at the beginning of an expansion portion of a cycle and the other clamped pair is energized at the end of the expansion portion, holding the rod clamped at both ends in its extended condition, then the rod can be made to move in either direction by selectively releasing one of the pairs of clamps before the field collapse as the electric current reaches its maximum value. By controlling the relationship between the application of the voltage to the winding and the clamping and releasing of the various clamped pairs, movement of the magnetostrictive rod in a selected direction can be achieved.